Centrifuge for spraying liquid material to be prilled

ABSTRACT

Centrifuge for use in spraying liquid material intended to be converted into so-called prills. The centrifuge comprises a centrifuge container having a perforated wall, a displacement body arranged in said container and means for rotating the container. Liquid material to be sprayed is supplied through a pipe, either to the annular space between the displacement body and the perforated wall of the centrifuge container, or to the inner space of a hollow displacement body having orifices through which the liquid material can flow out in the space between the body and the perforated wall of the centrifuge container. The displacement body may be mounted axially moveable and/or rotatable independently of the centrifuge container.

United States Patent [72] Inventor Isak Andreas F riestad [56]References Cited Flattenlia. Norway UNITED STATES PATENTS g 313132.779473 1/1957 Wezel 2l0/2l3(X) [45] Patented Feb. 9, 1971 PrimaryExaminerLloyd L. King [73] Assignec Norsk Hydro-Elektrisk AssistantExaminer-Gene A. Church Kvaelstofaktieselskab Att0rney Wenderoth, Lind &Ponack Oslo, Norway [32] Priority Oct. 25, I967 3 1 Norway ABSTRACT:(centrifuge for use in spraying liquid material in- 3 170,270 tended tobe converted into so-called prills. The centrifuge [54] CENTRIFUGE FORSPRAYING LIQUID MATERIAL TO BE PRILLED 8 Claims, 2 Drawing Figs.

[52] US. Cl 239/222, 210/213; 239/103 [51] Int. Cl B05b 3/02 [50] Fieldof Search 239/222,

214.19, 225, 230, 260, 381; 2IO/2l3 comprises a centrifuge containerhaving a perforated wall, a displacement body arranged in said containerand means for rotating the container. Liquid material to be sprayed issupplied through a pipe, either to the annular space between thedisplacement body and the perforated wall of the centrifuge container,or to the inner space of a hollow displacement body having orificesthrough which the liquid material can flow out in the space between thebody and the perforated wall of the centrifuge container.

The displacement body may be mounted axially moveable and/or rotatableindependently of the centrifuge container.

PATENTEU FEB 9 i971 Fae INVENTOR ISAK ANDREAS FRIESTAD l llfl I IliiilillliilllillIlill'li15lllIIIIIIIIIIUflII HHHI'HIi' ii ATTORNEYSCENTRIFUGE FOR SPRAYING LIQUID MATERIAL TO BE PRILLED The presentinvention relates to a centrifuge for use in spraying liquid materialintended to converted into so-called prills.

This process, so-called prilling," consists in liquid material, whichfor instance can be molten material or a concentrated solution and inwhich solid particles may be dispersed being ejected through theperforated wall of a centrifuge. In this way the sprayed material isdivided into droplets which can be caused to solidify by falling througha gas or a liquid.

Prilling is especially used for concentrated molten fertilizers with lowwater content comprising amongst others suspensions containing the planenutrients N and P, in which may also be suspended or dispersed solidmaterials such as potassium salts, magnesium salts and micronutrients.

The spraying of the above-mentioned liquid materials through aperforated centrifuge wall presents many problems, primarily due to theclogging or filling of the orifices in the centrifuge wall. This appliesin particular to liquid materials of high viscosity and which besidescontain suspended or dispersed solid particles. Such mixtures often havepseudo plastic properties which increases the difficulty of spraying.

The problems concerned with clogging or filling of the orifices can bereduced by increasing the diameter of the orifices. As the output perorifice in a centrifuge will thus increase, the speed of rotation has tobe increased in order to maintain a desired grain size. However, thisresults in an increased distance to which the particles are thrown andthe dimensions of the solidifying tower have to be increased beyondeconomical limits if it is desired to avoid the tower walls being coatedwith solidified material.

The present invention now relates to a centrifuge for use in prillingliquid material, for example concentrated molten fertilizers with a lowwater content as above mentioned, in which centrifuge the abovementioned problems are eliminated or at least reduced to a substantialdegree.

A centrifuge according to the invention is substantially characterizedby a displacement body arranged in the centrifuge container, the surfaceof said body facing the perforated wall of the centrifuge containerhaving substantially the same rotational shape as the wall of thecentrifuge container and being concentric with the same.

The distance between the centrifuge wall and the displacement bodyshould preferably not be more than 20 mm. and can preferably be from 2 lmm.

According to a preferred embodiment of the invention the displacementbody is stationary, but it is also possible to mount it on a shaft whichis rotatable independently of the centrifuge container.

The liquid material to be prilled can be supplied to the annular spacebetween the perforated centrifuge wall and the displacement body at theupper or lower end of the same. It is, however, also possible to supplythe liquid material to the interior of a hollow displacement body and tolet the material flow out through orifices in the wall of thedisplacement body.

In order that the invention may be more easily understood it will bedescribed in more detail with reference to the accompanying drawingshowing diagrammatically two embodiments of centrifuges according to theinvention in axial section.

FIG. I is an axial cross-sectional view of one embodiment of theinvention.

FIG. 2 is a similar view of another embodiment of the invention.

In FIG. 1, numeral 1 designates a centrifuge container which can be of aperformance known per se. The centrifuge container is attached to ashaft 2, which can be set in rotation at a suitable speed, for instance500 to 1500 rev./min.

The conical wall la of the centrifuge container is perforated in usualmanner. The perforations are not shown in the draw- Three designates adisplacement body which according to the invention is arranged in theinterior of the centrifuge container. The side of the displacement bodyfacing the perforated wall of the centrifuge container is provided witha surface which is substantially concentric with the perforated wall ofthe centrifuge container. The displacement body 3 is attached to atube-shaped body 4 surrounding the centrifuge shaft 2. 5 designatesorifices in the wall of the tube 4 just above the displacement body.Below these orifices, the inner side of the tube is provided with guidebafflcs 6 (for instance lips") serving to guide a part of the liquidmaterial out through the orifices 5.

Liquid material to be prilled is supplied to the centrifuge containerthrough the annular intermediate space 7 between tube 4 and shaft 2. Thetube 4 is open at the lower end so that the liquid material will flowout into the centrifuge container at the bottom of the same and thenflow upwardly through the annular intermediate space between theperforated wall Ia of the centrifuge container and the displacement body3.

Part of the liquid material will as above mentioned flow out through theorifices 5 and then flow outwards and downwards to the upper end of theannular spacebetween the wall la and the displacement body 3.

The orifices 5 may be omitted if desired.

The embodiment according to FIG. 2 deviates from the embodimentaccording to FIG. 1 mainly in that the liquid materi' al is supplied tothe inside of a hollow displacement body. ln this FIG. 1. la and 2designate corresponding parts to those in H6. 1.

3a is a displacement body, which in H0. 2 is made hollow. The wall 3!;facing the perforated wall la of the centrifuge container is providedwith orifices or slots 3c.

The displacement body is attached to a tube 4a surrounding thecentrifuge shaft 2. The tube 40 can be stationary or may be rotatablymounted independently of the shaft 2.

At the upper end the displacement body 3a is provided with a cylindricalwall 8 surrounding the tube 4a at some distance from the same. Theliquid material is supplied to the centrifuge through the annularintermediate space 9 between the tube 4a and the wall 8. The liquidmaterial flows through this intermediate space down to the hollowdisplacement body and flows out through the orifices 3c to theintermediate space between the displacement body and the perforated wallla of the centrifuge container. t

lclaim:

l. A centrifuge suitable for spraying liquid material, which may havedispersed solid particles therein so as to form droplets, comprising aperforated container through which in operation the material is sprayed,a displacement body in said container, the surface of said body facingthe perforated wall of said container having substantially the samerotational shape as the said wall and being substantially concentrictherewith, and means for rotating the centrifuge container.

2. A centrifuge as claimed in claim 1, wherein the distance between theperforated wall of the centrifuge container and the said surface of thedisplacement body is not more than 20 3. A centrifuge suitable forspraying liquid material, which may have dispersed solid particlestherein so as to form droplets comprising a perforated container throughwhich in operation the material is sprayed, a displacement body in saidcontainer, the surface of said body facing the perforated wall of saidcontainer having substantially the same rotational shape as the saidwall and being substantially concentric therewith, means for rotatingthe centrifuge container and a supply pipe for liquid material to besprayed, said pipe communicating with the annular space between thecentrifuge wall and the displacement body.

4. A centrifuge suitable for spraying liquid material so as to formdroplets, comprising a perforated container through which in operationthe material is sprayed, a hollow displacement body in said container,the surface of said body facing the perforated wall of the centrifugecontainer having substantially the same rotational shape as said walland being concentric therewith, the wall of the hollow displacement bodybeing provided with orifices through which liquid material can flow fromthe inner space of the displacement body into the annular space betweenthe said body and the perforated wall of the centrifuge container, meansfor supplying liquid material to the inner space of the displacementbody, and means for rotating the centrifuge container.

5. A centrifuge suitable for sprayingliquid material so as to formdroplets, comprising a vertically mounted, rotatable shaft, means forrotating the shaft, a centrifuge container rigidly mounted on saidshaft, said container having a perforated wall having an increasingcross section from the lower end upwardly, a displacement body in saidcontainer, the surface of said body having substantially the samerotational shape as the perforated wall of the centrifuge container, and

2. A centrifuge as claimed in claim 1, wherein the distance between theperforated wall of the centrifuge container and the said surface of thedisplacement body is not more than 20 mm.
 3. A centrifuge suitable forspraying liquid material, which may have dispersed solid particlestherein so as to form droplets comprising a perforated container throughwhich in operation the material is sprayed, a displacement body in saidcontainer, the surface of said body facing the perforated wall of saidcontainer having substantially the same rotational shape as the saidwall and being substantially concentric therewith, means for rotatingthe centrifuge container and a supply pipe for liquid material to besprayed, said pipe communicating with the annular space between thecentrifuge wall and the displacement body.
 4. A centrifuge suitable forspraying liquid material so as to form droplets, comprising a perforatedcontainer through which in operation the material is sprayed, a hollowdisplacement body in said container, the surface of said body facing theperforated wall of the centrifuge container having substantially thesame rotational shape as said wall and being concentric therewith, thewall of the hollow displacement body being provided with orificesthrough which liquid material can flow from the inner space of thedisplacement body into the annular space between the said body and theperforated wall of the centrifuge container, means for supplying liquidmaterial to the inner space of the displacement body, and means forrotating the centrifuge container.
 5. A centrifuge suitable for sprayingliquid material so as to form droplets, comprising a vertically mounted,rotatable shaft, means for rotating the shaft, a centrifuge containerrigidly mounted on said shaft, said container having a perforated wallhaving an increasing cross section from the lower end upwardly, adisplacement body in said container, the surface of said body havingsubstantially the same rotational shape as the perforated wall of thecentrifuge container, and being substantially concentric therewith.
 6. Acentrifuge as claimed in claim 5 comprising a second vertically mounted,rotatable shaft on which the displacement body is rigidly mounted, andmeans for rotating said second shaft independently of the rotation ofthe shaft on which the centrifuge container is mounted.
 7. Centrifuge asclaimed in claim 1 wherein the distance between the displacement bodyand the centrifuge wall is from 2- 10 mm.
 8. Centrifuge as claimed inclaim 4 wherein the distance between the displacement body and thecentrifuge wall is from 2- 10 mm.